644024320 has 96 divisors (see below), whose sum is σ = 1562160600. Its totient is φ = 254803968.

The previous prime is 644024317. The next prime is 644024321. The reversal of 644024320 is 23420446.

It can be written as a sum of positive squares in 4 ways, for example, as 643941376 + 82944 = 25376^2 + 288^2 .

It is not an unprimeable number, because it can be changed into a prime (644024321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1115872 + ... + 1116448.

Almost surely, 2^644024320 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644024320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (781080300).

644024320 is an abundant number, since it is smaller than the sum of its proper divisors (918136280).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644024320 is a wasteful number, since it uses less digits than its factorization.

644024320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 713 (or 693 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 25.

The square root of 644024320 is about 25377.6342475023. The cubic root of 644024320 is about 863.5763812685.

Adding to 644024320 its reverse (23420446), we get a palindrome (667444766).

The spelling of 644024320 in words is "six hundred forty-four million, twenty-four thousand, three hundred twenty".